PROJECT SUMMARY/ABSTRACT This proposal, ?Assay Development of the MCL35 for Mantle Cell Lymphoma (MCL),? is written to validate a prognostic assay for MCL based on quantification of a proliferation signature using digital gene expression analysis. MCL is a B cell malignancy with a broad spectrum of clinical, pathological and biological features. MCL is defined by the t(11;14)(q13;q32) translocation, which results in over expression of the cyclin D1 protein and cell cycle dysregulation. MCL cases have markedly variable clinical behavior ranging from indolent to highly aggressive disease, with treatment options ranging from watchful waiting to high dose chemotherapy and stem cell transplant. The current approach to treatment is based largely on the patient's age at diagnosis and currently there is no therapeutic standard. Previously, our research consortium, the Lymphoma and Leukemia Molecular Profiling Project (LLMPP) analyzed snap frozen MCL tissue biopsies using gene expression profiling (GEP) and identified a ?Proliferation Signature? as the most powerful biomarker correlating with patient survival in MCL. However, the original techniques using frozen tissues and GEP were impractical for routine diagnostics. A potentially easy solution has been to use immunohistochemistry on tissue biopsies to assess the presence of the Ki67 antigen as a global marker of cell proliferation. Ki67 studies have been prognostic in multiple studies using various thresholds; however, there are serious issues with reproducibility between different lab techniques and Pathologists' approach to interpretation. Therefore, as part of our work in the National Cancer Institute's SPECSII program, we developed a novel GEP proliferation signature assay for MCL that works well in formalin-fixed, paraffin-embedded tissues (FFPET) called the ?MCL35?. The MCL35 uses the clinical-grade NanoString nCounter system, which is FDA-approved as the technical platform for the ProSigna Breast Cancer assay. The MCL35 is accurate, reproducible, with an inter-lab reproducibility of 100% in our initial work, making it a strong candidate for application in the clinical diagnostic setting. The MCL35 assay has gained attention since first being orally presented at the American Society of Clinical Oncology in June 2016, and we are in discussions with pharmaceutical companies and clinical trial cooperative groups on applications for the assay. The goals of the current project are first to thoroughly analytically validate the MCL35 (UH2 phase); then, use the refined assay to retrospectively interrogate clinical trial cohorts to establish it's clinical validity (UH3 phase). The long term goal is to use the resulting refined and validated MCL35 to prospectively identify those MCL patients in need of immediate curative intent therapy in order to design clinical trials around this high risk subset and improve patient survival.